[Beowulf] NFS over RDMA performance confusion
landman at scalableinformatics.com
Thu Sep 13 09:05:36 PDT 2012
On 09/13/2012 11:21 AM, holway at th.physik.uni-frankfurt.de wrote:
>> I assume so, but just to be clear you witnessed this behavior even with
>> the -I (directio) parameter?
> for i in 1 2 4 8 16; do /cm/shared/apps/iozone/current/sbin/iozone -I -l
> $i -u $i -r 16k -s 10M -F file1..file16 ; done > output &
-s 10M ???
This is a 10M test file size.
Ok. Let me be clear, 10M as a file size is not useful as a test. The
numbers are, for lack of any better way to describe this, meaningless.
From the iozone man page
-s # Used to specify the size, in Kbytes, of the file to
may also specify -s #k (size in Kbytes) or -s #m
Mbytes) or -s #g (size in Gbytes).
If each storage node has 128GB ram (I think this was the number) and you
want a "serious" (as in real) test, you need to take your N storage
nodes @128GB each, sum up the ram, double it, and that is your file
size. When you have that, your performance numbers will be uncached,
and therefore far more likely to represent the actual hardware performance.
Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics Inc.
email: landman at scalableinformatics.com
web : http://scalableinformatics.com
phone: +1 734 786 8423 x121
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